Count me in the minority of people that think JJJ has a fairly low ceiling. I mainly see him as a pretty good starter. At best, he looks like a young Ibaka to me.
His rebounding numbers at MSU and in Memphis have not been good. His block rate is a bit lower than I thought would be. His offensive game is not refined. He has little feel. He's a good shooter and can sometimes get a little hookshot over his left shoulder, but other than that, he really isn't a scorer. On top of that, his form restricts his ability to develop one-dribble pullups, fade aways, or any of the other shots that make a guy hard to stop.
He's fine. Really. But this isn't a trade that makes a ton of sense for anyone.
He's still 19 now, after a full season in the NBA. He scored 14 ppg fairly efficiently in 26 mpg. He's just about as good as Ibaka is now, in his prime. Anthony Davis posted slightly better stats his rookie year.
NBA players are very rarely any good until they are 23-24, even when they end up as all-stars.
Placing a ceiling on anyone before age 24 is unwise. At minimum, Jackson will very likely make several all-star teams.
14 ppg game on a 20 win team has to be taken in context. Tony Wroten had 13 ppg as a 20 year old on less minutes, but was out of the league a few years later.
I'm not basing my evaluation on ppg. 14 ppg in the NBA is impressive in its own right. How did he score? He was playing next to two of the best passers/facilitators in the NBA in Conley and Gasol. They got him great looks and he converted. Good for him.
My point is not that he stinks or anything. My point is about his style that might lower his floor. Jayson Tatum averaged more rebounds per 100 possessions than Jackson.
Jackson has also always had a serious problem with fouls (7.2 per 100 possessions!) -- that's something that a lot of young bigs struggle with, but that needs to be overcome before he can be a reliable defensive anchor.
He is effective in how he scores right now, but I'm not convinced he can score much more than he is. Maybe he can, but I don't see a real natural feel on offense, and there's no doubt that his shooting form restricts a lot of scoring moves that would take him to the next level as a scorer.
Again, my point is not that he is a bad player. He's a good young big, but I'm not as high on him as some. There's real holes to his game that lower his ceiling in my mind, but we will see if I'm right.